Devices in the field of the present invention are used to place ink below the surface of an object or article. A pin or needle punctures the surface and places the ink below the surface. When the surface is the skin of a living being, and the ink does not react with the skin, the ink is placed at such a level in the skin, where it remains permanently. Because the ink is permanent, it is very important that the ink be applied very precisely. Correspondingly, it is very important that the position of the needle when it punctures the surface, can be precisely controlled. The needle must be moved back and forth in a reciprocating motion in order to puncture the surface, and this motion must be very limited in a direction perpendicular to the reciprocating motion.
U.S. Pat. No. 4,782,725 to Spaulding, describes an article identification device in the same field as the present invention, where the needle is reciprocated by an offset pin on the rotor of a motor. The offset pin is attached to an armature which slides in a slot. The needle is connected to the armature. In order to make the device light weight, the housing of the device, which defines the slot, and the armature are formed of a plastic. Due to the characteristics of plastic, tolerances between the armature and the slot in the housing have to be very large in order for the armature to slide easily in the slot. Plastic is also known to have a high thermal coefficient of expansion, such that the plastic expands and contracts greatly with temperature. Therefore, tolerances must be made extra large to compensate for expansion. The needle and armature oscillate in the reciprocating motion in the range of thousands of RPM or Hertz. Therefore, with continuous use, the plastic armature and slot receive much wear. This further increases the tolerance between the armature and the slot. While limiting movement of the needle in a plane perpendicular to the reciprocating motion is possible by the armature of Spaulding, it cannot be limited to more than the tolerance between the armature and the slot.